Refrigerator having a drying function, and operating method therefor

ABSTRACT

A refrigerator contains a storage compartment, a heat exchanger chamber separate from the storage compartment, a heat exchanger which can be operated as an evaporator or as a heating unit, a fan for driving an exchange of air between the storage compartment and the heat exchanger chamber, and a control unit for controlling the operation of the heat exchanger, the fan and the heating unit. The control unit assists a drying operating mode in which the fan operates at the same time as the heating unit.

The present invention relates to a refrigerator having a drying function, i.e. a refrigerator which is able to dry stored material, in particular food, rapidly and effectively and a method for drying material in the refrigerator.

To a certain extent almost all refrigerators tend to dry out refrigerated goods stored therein, since moisture evaporated from the refrigerated goods tends to condense on an evaporator and thus is lost from the refrigerated goods. This effect is particularly apparent in frost-free refrigerators in which refrigerated goods and evaporators are spatially separated from one another. In particular unpackaged leafy vegetables, therefore, tend to wither rapidly in a frost-free refrigerator but on the other hand the drying out is not intensive enough in order to permit a targeted drying of food.

In many frost-free refrigerators a heating unit is provided in an evaporator chamber in order to defrost the evaporator. This heating unit is only in operation if the evaporator is not cooling at the same time and if a fan, which in normal cooling mode circulates air between the evaporator chamber and the storage compartment, is also switched off.

A refrigerator in which a heating unit is arranged in a storage compartment in order to dry the contents of the storage compartment is disclosed in JP 2008032392. However, the efficiency of this drying is limited. Nothing is disclosed about the positioning of the heating unit in the storage compartment but it is assumed from the drawing that it is located on the floor of the storage compartment. If the compartment is completely filled up, the result of this is that the heat initially has to spread through the dry goods to the surface thereof so that it may assist with the evaporation there; at the same time heat is lost in the downward direction. Attaching the heating unit above the dry goods is also unsatisfactory since then the cold air blown into the compartment separates the heating unit and the dry goods from one another.

It is the object of the present invention to provide a refrigerator which by means of a simple construction permits efficient drying of stored material and to specify an operating method for such a refrigerator.

In the case of a refrigerator comprising a storage compartment, a heat exchanger chamber separate from said storage compartment and containing a heat exchanger which can be operated as an evaporator and a heating unit, a fan for driving the exchange of air between the storage compartment and the heat exchanger chamber, and a control unit for controlling the operation of the heat exchanger, fan and heating unit, the object is firstly achieved by the control unit assisting a drying operating mode in which the fan operates at the same time as the heating unit. In this manner, the heating unit may not only be used for defrosting the heat exchanger but also by the input of heat into the storage compartment for increasing the evaporation there.

Since, in the drying operating mode, heating phases in which the fan is in operation at the same time as the heating unit alternate with cooling phases in which the heat exchanger as an evaporator and the fan are in operation at the same time, moisture which is discharged from the material in the storage compartment during the course of a heating phase may be condensed in a subsequent cooling phase on the heat exchanger and thus be permanently removed from the material.

Between a cooling phase and a subsequent heating phase the control unit is designed to insert a defrosting phase in which the heating unit is in operation without the fan, so that frost condensed out on the heat exchanger is able to defrost and drain away, without an airflow passing thereover being able to convey vapor back to the storage compartment.

The control unit is then designed to transfer from the defrosting phase to the heating phase, i.e. set the fan in operation, when the rise of the temperature of the heat exchanger from a negative to a positive value enables it to be deduced that the heat exchanger is completely defrosted.

The control unit may be connected to a hygrometer arranged in the storage compartment, in order to decide from the measured data thereof when the material in the storage compartment is sufficiently dry that the drying operating mode may be terminated.

It is possible to deduce from the duration of the defrosting phase the quantity of frost condensed on the heat exchanger and thus the degree of drying of the material in the storage compartment; which is why the control unit may be expediently designed to detect the duration of the defrosting phase and to terminate the drying operating mode if this duration falls below a threshold value. Thus the hygrometer may become superfluous in the storage compartment.

This threshold value may be fixedly predetermined, i.e. the same for each drying process. It is more advantageous, however, to fix this value individually in proportion with the quantity of the material to be dried and the drying properties thereof for each drying process. This may be carried out in a simple manner by the duration of the first defrosting phase of a drying process being measured and the threshold value being fixed as a function of this duration, in particular as a predetermined fraction thereof. Thus substantially irrespective of the quantity of the material stored in the storage compartment it may be ensured that during the course of the drying process the water content of the material is reduced corresponding to the fraction.

The tendency of the material to discharge water is dependent on many different factors which combined together may be described as type of material, such as for example its biological origin (meat, mushrooms, fruit, leaves), the type of preparation (such as waxed, roughly or finely chopped, with or without the skin), etc. In order to estimate this tendency and when making a decision about when it is possible to consider terminating the drying process, the control unit may also be connected to a storage compartment temperature sensor and designed to detect the alteration speed of the temperature of the storage compartment. The alteration speed may be determined as a difference between the temperatures measured in a predetermined time interval; on the other hand, the time required for a predetermined temperature alteration, in particular the duration of a heating phase and/or a cooling phase, may also be measured. The alteration speed provides information about the quantity of material; if this is set in relation to the quantity of water discharged from the material in a cooling phase, this makes it possible to deduce the tendency of the material to discharge water and may be taken into account when fixing a condition for terminating the drying process. In particular, the threshold value may be fixed at a lower level for the duration of the defrosting phase, the greater the tendency of the material to discharge water.

In order to be able to estimate the tendency of the material to discharge water, the control unit may also be connected to a user interface and designed to receive therefrom an input from a user about the type of material loaded into the storage compartment.

The control unit may also be connected to a set of scales which is arranged in the storage compartment in order to weigh the material loaded into the storage compartment. Such a set of scales may simplify the drying in different ways. Firstly, the weight of the material may be continuously monitored and the drying process terminated if the weight has reduced to a predetermined fraction of the initial weight of the material. How large this fraction is to be may be established by using the type of material, if known. On the other hand, from the weight and the speed of the weight reduction conclusions may be drawn about the type of material, and a target weight at which the drying process is terminated may be established in a suitable manner.

According to a preferred embodiment, the heat exchanger is able to be switched between operation as an evaporator and operation as a heating unit.

To this end, in a refrigerant circuit the heat exchanger may be connected in series to at least one throttle point, the throughflow rate thereof being controlled by the control unit.

This embodiment permits, in particular, energy-efficient drying when the refrigerator comprises at least one further storage compartment, the heat released during operation of the heat exchanger as a heating unit being able to be discharged therefrom.

Expediently, the control unit is further designed to transmit a message about the termination of the drying operating mode to a networked appliance which immediately informs the user thereof about the termination of the drying process by a—preferably acoustic or tactile-signal. After emitting this signal, an explanation which provides information about the termination of the drying process may be retrieved on a screen of the networked appliance. By subsequently emptying and refilling the storage compartment, the user may then fully utilize the drying capacity of the appliance, and at the same time the user may move away from the refrigerator during a drying process and complete other tasks. A suitable utility program for receiving the message and generating the signal, such as for example an app for a smartphone, may be delivered or provided for download as an accessory for the refrigerator according to the invention.

The object is further achieved by a method for drying material in a refrigerator, in particular a refrigerator as described above, having the steps

a) introducing the material into a storage compartment of the refrigerator; and

b) circulating air between the storage compartment and a chamber in which the air is alternately heated in a heating phase and is cooled in a cooling phase by a heat exchanger operated as an evaporator.

A further solution of the object is a method for drying material in a refrigerator, having the steps

a) introducing the material into a storage compartment of the refrigerator which is able to be temperature-controlled by a heat exchanger;

b) alternately operating the heat exchanger as an evaporator and as a condenser.

The drying may be terminated if at least one of the following parameters has reached a threshold value

-   -   air humidity in the storage compartment     -   duration of the drying process     -   weight of the material     -   duration of a heating, cooling or defrosting phase of the heat         exchanger.

This threshold value may be fixed using an initial value of at least one of the cited parameters and/or the type of material.

Further features and advantages of the invention are disclosed from the following description of exemplary embodiments with reference to the accompanying figures, in which:

FIG. 1 shows a schematic section through a refrigerator according to the invention;

FIG. 2 shows a refrigerant circuit of the refrigerator; and

FIG. 3 shows a flow diagram of an operating method executed by a control unit of the refrigerator.

FIG. 1 shows in a schematic sectional view a part of a housing 1 of a refrigerator. In addition to a chamber 2 which is shown in its entirety, one or more chambers 3 which are shown only in a fragmentary manner in the figure may be present. The chamber 2 is subdivided by an intermediate wall 4 into a heat exchanger chamber 5 and a storage compartment 6. The heat exchanger chamber 5 contains, in a manner known per se, a heat exchanger 7 which may be operated as an evaporator for cooling the storage compartment 6 and a fan 8 for driving an airflow 9 which circulates through the heat exchanger chamber 5 and the storage compartment 6. The storage compartment 6 is able to be loaded with material 11 to be dried.

An electrically operated defrost heater, which is known per se, may be mounted on the heat exchanger 7. Preferably, however, alternatively the heat exchanger 7 itself is able to be operated optionally as an evaporator or as a condenser discharging heat to the heat exchanger chamber 5, as is described below in more detail.

A collection channel 16 for condensed water draining from the heat exchanger extends on the floor of the heat exchanger chamber 5 below the heat exchanger 7. A condensed water drain 17 leads from the lowest point of the collection channel 16 through an insulation layer surrounding the chamber 2 to an evaporation tray 18. The evaporation tray 18 may be arranged in a machine chamber of the refrigerator closely adjacent to a compressor 19 in order to be heated by the waste heat thereof.

An electronic control unit 10 is connected to a heat exchanger temperature sensor 12 which is mounted on the heat exchanger 7 and to a storage compartment temperature sensor 13 on a wall of the storage compartment 6.

Optionally, the control unit 10 may be connected to a hygrometer 14 which is arranged on the path of the airflow 9, preferably at an inlet of the heat exchanger chamber 5.

Furthermore, a set of scales 15 which may be loaded with the material 11 to be dried may optionally be provided in the storage compartment 6 in order to deliver measured values of the weight thereof to the control unit 10. The set of scales 15 may be a domestic set of scales which may also be operated autonomously outside the refrigerator and which is placed in the storage compartment 6 and connected to the control unit 10 merely for drying the material 11.

FIG. 2 shows a refrigerant circuit according to a preferred embodiment of the refrigerator. Initially, a condenser 21 which is exposed on the outside of the body 1 is connected to a refrigerant line 20 starting from a pressure connection of the compressor 19. Downstream of the condenser the line 20 forks into two branches 22, 23. A first controllable throttle point 24, the heat exchanger 7 and a second controllable throttle point 25 are connected in series on the branch 22, and a third controllable throttle point 26, a heat exchanger 27 of one of the chambers 3 and a fourth controllable throttle point 28 are connected in series on the branch 23. The line 20 extends from a joining point of the two branches 22, 23 via an evaporator 29 of a further compartment 3 to a suction connection of the compressor 19. The throttle points 24, 25, 26, 28 may be expansion valves. The flow conductance thereof is able to be adjusted by the control unit 10.

If, when the compressor 19 is operating, the flow conductance of the throttle point 24 is low but that of the throttle point 25 is high, the pressure drops substantially at the throttle point 24 and the pressure in the heat exchanger 7 is sufficiently low in order to reach an evaporation temperature of below 0° C. at that point. If, however, the throttle point 24 is wide open and the throttle point 25 is set to be narrow, the pressures in the condenser 21 and in the heat exchanger 7 are substantially equal. Since the heat exchanger 7 is cooler than the condenser 21, condensation is generated substantially in the heat exchanger 7 and the heat released thereby is transferred by the airflow 9 into the storage compartment 6. This heat is removed from the compartment 3 of the evaporator 29 since the refrigerant evaporates again at that point.

FIG. 3 shows an operating method of the control unit 10. A drying process starts by a user inputting a corresponding command at a user interface 30 (S1). The control unit 10 initiates a cooling phase S2 by switching the throttle point 24 to low conductance, the throttle point 25 to high conductance and operates the compressor 19 and the fan 8. The heat exchanger 7 cools down to a temperature below 0° C. and cold air from the heat exchanger 7 reaches the storage compartment 6. In the meantime, warm air suctioned from the storage compartment discharges its moisture as frost on the heat exchanger 7. This state is maintained until the storage compartment temperature sensor 13 indicates that the temperature has fallen below a lower threshold temperature Tmin. In order to prevent freezing of the material 11 in the storage compartment 6, the lower threshold temperature Tmin should be selected to be above 0° C.

If the temperature has fallen below a cut-off threshold temperature, in step S3 a test may be carried out to establish whether conditions for terminating the drying process are fulfilled. These conditions may be different depending on which sensors the refrigerator is provided with, and are described below.

If these conditions are not fulfilled, the throttle point 24 is switched to high conductance and the throttle point 25 to low conductance. The compressor 19 remains in operation so that the refrigerant condenses in the heat exchanger 7 instead of evaporating. Meanwhile, the fan 8 may remain in operation: but preferably it is initially switched off in order to heat the heat exchanger 7 in a defrosting phase S4 until the heat exchanger temperature sensor 12 displays a positive temperature of the heat exchanger 7. If this is the case, the frost from the heat exchanger 7 is defrosted and the water is drained out via the condensed water drain 17. In the following heating phase the fan 8 blows warm air from the heat exchanger 7 into the storage compartment 6. The storage compartment 6 and the material 11 therein are warmed until an upper threshold temperature Tmax is exceeded. This upper threshold temperature Tmax may be adjustable on the user interface 30 or fixed to the type of material 11 by the control unit 10 using inputs provided at the user interface 30; in order to achieve rapid drying, it should be possible to set an upper threshold temperature Tmax above room temperature, preferably above 40 or even 50° C.

In the case of FIG. 3, when the upper threshold temperature Tmax is exceeded the method immediately returns to step S2. Alternatively, at this point the test could be carried out to establish whether the conditions for terminating the drying process are fulfilled.

In the simplest case when the hygrometer 14 is present, the terminating condition may be when the air humidity falls below a threshold value. Such a threshold value may be predetermined differently according to the type of material 11 to be dried, and stored in a storage device, the control unit 10 retrieving said threshold value using data from the user relative to the material 11.

As a further condition, it may be provided to terminate the drying process when the air humidity at the termination of the cooling or heating phases does not alter during the course of a plurality of cycles of the method or when the total duration of the drying process has reached a permitted maximum value.

If the set of scales 15 is present, the control unit may terminate the drying process when the weight of the material 11 has reduced to a fraction of the weight at the start of the drying process—preferably predetermined according to the type of material 11—or when the weight no longer alters during the course of one cycle of the method.

According to a development, during the course of a defrosting phase S4 the control unit measures the defrosting time which the heat exchanger requires in order to be heated from a predetermined temperature just below 0° C. to a temperature just above 0° C. This time is a measurement of the quantity of frost collected in the previous cooling phase. If it is shorter than a predetermined threshold value then the material 11 may be regarded as dry and the drying process terminated.

When fixing this threshold value, the quantity of material 11 loaded in the storage compartment 6 should be considered: the greater this quantity of material, the greater the quantity of frost which then condenses on the heat exchanger 7 if the material is already dried to the required extent. This is why according to a second development the control unit also measures the duration of the cooling phase. This is linearly dependent on the quantity of material 11. Thus, in particular, the quantity of material may be estimated from the duration of the first cooling phase and the threshold value of the defrosting time may be proportionally fixed to this quantity of material.

It is also conceivable to draw conclusions about the weight loss of the material 11 from the shortening of the cooling phases during the course of a drying process, and to terminate the drying process when this weight loss has reached a predetermined fraction of the initial weight.

The ratio between the quantity of material estimated using the duration of a cooling phase and the quantity of water estimated using the defrosting time of the subsequent heating phase enables the control unit 10 to identify whether the material 11 which is located in the storage compartment is easy or difficult to dry. In the case of material with a large surface area which is easy to dry, the water loss in each cycle is high and the control unit may also set the threshold value of the defrosting time, at which it terminates the drying process, to be correspondingly high. In the case of material which is difficult to dry, such as for example fruit protected from drying out by a skin, with the same quantity of material a significantly lower threshold value of the defrosting time has to be selected in order to ensure sufficient drying out.

The refrigerator may have a network interface 31, for example to a WLAN or cellular network, via which the control unit 10 transmits a message to a networked appliance, such as a smartphone of the user in order to inform the user when the drying process is complete and the material 11 may be removed from the storage compartment 6 and replaced by fresh material.

A special app may be installed on the networked appliance in order to process the message of the control unit 10. The processing may consist of immediately producing a—preferably acoustic or haptic—signal which the user is able to perceive without having to look at the networked appliance, and providing information which may be read by the user on a screen of the networked appliance, when the user activates the screen having been informed thereof by the signal. However, it is also possible to register the refrigerator as a subscriber in a text messaging service, which is known per se, such as SMS or WhatsApp and to use this text messaging service in order to transmit the message to the networked appliance.

LIST OF REFERENCE NUMERALS

-   1 Housing -   2 Chamber -   3 Chamber -   4 Intermediate wall -   5 Heat exchanger chamber -   6 Storage compartment -   7 Heat exchanger -   8 Fan -   9 Airflow -   10 Control unit -   11 Material -   12 Heat exchanger temperature sensor -   13 Storage compartment temperature sensor -   14 Hygrometer -   15 Set of scales -   16 Collection channel -   17 Condensed water drain -   18 Evaporation tray -   19 Compressor -   20 Refrigerant line -   21 Condenser -   22 Branch -   23 Branch -   24 Throttle point -   25 Throttle point -   26 Throttle point -   27 Heat exchanger -   28 Throttle point -   29 Evaporator -   30 User interface -   31 Network interface 

1-15. (canceled)
 16. A refrigerator, comprising: a storage compartment; a heat exchanger chamber separate from said storage compartment; a heat exchanger which can be operated as an evaporator and as a heating unit and disposed in said heat exchanger chamber; a fan disposed in said heat exchanger chamber for driving an exchange of air between said storage compartment and said heat exchanger chamber; and a control unit for controlling an operation of said heat exchanger, said fan and said heating unit, said control unit assisting a drying operating mode in which said fan operates at a same time as said heating unit.
 17. The refrigerator according to claim 16, wherein in the drying operating mode, heating phases in which said fan is in operation at the same time as said heating unit alternate with cooling phases in which said heat exchanger functioning as said evaporator and said fan are in operation at a same time.
 18. The refrigerator according to claim 17, wherein between a cooling phase and a subsequent heating phase said control unit is configured to initiate a defrosting phase in which said heating unit is in operation without said fan.
 19. The refrigerator according to claim 18, further comprising a heat exchanger temperature sensor; and wherein said control unit is connected to said heat exchanger temperature sensor and is configured to transfer from the defrosting phase to the heating phase when a temperature of said heat exchanger has risen from a negative to a positive value.
 20. The refrigerator according to claim 18, wherein said control unit is configured to detect a duration of the defrosting phase and to terminate the drying operating mode if the duration falls below a threshold value.
 21. The refrigerator according to claim 16, further comprising a storage compartment temperature sensor; and said control unit is connected to said storage compartment temperature sensor and is configured to detect an alteration speed of a temperature of said storage compartment.
 22. The refrigerator according to claim 16, further comprising a user interface; and wherein said control unit is connected to said user interface and is configured to receive from said user interface an input from a user about a type of material loaded into said storage compartment.
 23. The refrigerator according to claim 22, further comprising a set of scales disposed in said storage compartment in order to weigh the material loaded into said storage compartment; and wherein said control unit is connected to said set of scales and uses a weight of the material, said control unit is configured to make a decision about a termination of the drying operating mode.
 24. The refrigerator according to claim 16, wherein said heat exchanger is able to be switched between operation as said evaporator and operation as said heating unit.
 25. The refrigerator according to claim 16, further comprising: at least one throttle point; and a refrigerant circuit, in said refrigerant circuit said heat exchanger is connected in series to said at least one throttle point, a throughflow rate of said throttle point being controlled by said control unit.
 26. The refrigerator according to claim 16, wherein said control unit is configured to transmit a message about a termination of an operating mode to a networked appliance.
 27. A method for drying material in a refrigerator, which comprises the steps of: introducing the material into a storage compartment of the refrigerator; and circulating air between the storage compartment and a heat exchanger chamber in which the air is alternately heated in a heating phase and is cooled in a cooling phase by a heat exchanger operated as an evaporator.
 28. The method according to claim 27, wherein a drying step is performed and the drying step is terminated if at least one parameter has reached a threshold value, the parameter being selected from the group consisting of air humidity in the storage compartment, a duration of a drying process, a weight of the material, and a duration of a heating phase, a cooling phase or a defrosting phase of the heat exchanger.
 29. The method according claim 28, wherein the threshold value is fixed using an initial value of at least one of the parameter and/or a type of material.
 30. A method for drying material in a refrigerator, which comprises the steps of: introducing the material into a storage compartment of the refrigerator which is able to be temperature-controlled by a heat exchanger; and alternately operating the heat exchanger as an evaporator and as a condenser. 